Hair of the Dog Dave Clone

Originally posted by puzzl
Donít you only need a few ounces to get it tested?

I think it would actually be really helpful to the community to have even this first data point to work with. This issue comes up over and over again, and to be able to say even for once instance "hey, this guy froze off 50% of a 10% beer and ended up with a 16% beer" would be extremely helpful.

Does anyone know where I could get this sort of testing done? Cost?

Looks like White Labs does it. They don’t mention a cost, but I’ve heard that it isn’t too expensive, like less than 20 bucks. I’d chip in 10 bucks towards the cost and I’m sure others here would too that are interested enough in the results.

Originally posted by puzzl
Looks like White Labs does it. They donít mention a cost, but Iíve heard that it isnít too expensive, like less than 20 bucks. Iíd chip in 10 bucks towards the cost and Iím sure others here would too that are interested enough in the results.

You are always assuming that there is no ethanol in the liquid left behind though, which is clearly false. The freezing point of ethanol isnít the question... whatís the freezing point of a 50% solution of water and ethanol... by your calculations, youíll tell me itís the average of -173 and 32, which it isnít.
Freezing points of ethanol-water mixtures (by volume) in degrees C

You donít just derive physical properties of mixtures from an average of the physical properties of the pure compounds. With sugar itís even more complicated because the freezing point of a sugar/water solution doesnít even vary in a straight line.

When you add ethanol to this mixture, the system becomes even more complicated and I canít find any information on it (although it has probably been done at some point).

a. I’m not assuming anything about the liquid that is left behind. Please show me where you think that I did.

b. By my calculations it would be the average of -173 and 32? Bullshit. Where exactly did I tell you anything about how I would calculate the freezing point?

c. "With sugar itís even more complicated because the freezing point of a sugar/water solution doesnít even vary in a straight line." Impressive display of misleading data! You must be in politics or journalism. Over the range of values that we’d care about, the freezing point of a sugar and water mixture is very predictable and well behaved.

d. I hadn’t bothered to calculate or look up the freezing point for ethanol/water mixtures yet, but looking at that table, it’s clear you would want to estimate the amount of sugar in the final product and adjust the water/sugar freezing point. Sure, this is only a first order calculation, but given the limitations of the temperature measurement, it’s going to be close enough.

If you really wanted to get an accurate measurement, it would be very easy to model the freezing point based on the FG and ABV, and all you would need is vodka, water, table sugar, an accurate thermometer and scale, and enough free time to take 50ish data points.

You are always assuming that there is no ethanol in the liquid left behind though, which is clearly false. The freezing point of ethanol isnít the question... whatís the freezing point of a 50% solution of water and ethanol... by your calculations, youíll tell me itís the average of -173 and 32, which it isnít.
Freezing points of ethanol-water mixtures (by volume) in degrees C

You donít just derive physical properties of mixtures from an average of the physical properties of the pure compounds. With sugar itís even more complicated because the freezing point of a sugar/water solution doesnít even vary in a straight line.

When you add ethanol to this mixture, the system becomes even more complicated and I canít find any information on it (although it has probably been done at some point).

a. Iím not assuming anything about the liquid that is left behind. Please show me where you think that I did.

b. By my calculations it would be the average of -173 and 32? Bullshit. Where exactly did I tell you anything about how I would calculate the freezing point?

c. "With sugar itís even more complicated because the freezing point of a sugar/water solution doesnít even vary in a straight line." Impressive display of misleading data! You must be in politics or journalism. Over the range of values that weíd care about, the freezing point of a sugar and water mixture is very predictable and well behaved.

d. I hadnít bothered to calculate or look up the freezing point for ethanol/water mixtures yet, but looking at that table, itís clear you would want to estimate the amount of sugar in the final product and adjust the water/sugar freezing point. Sure, this is only a first order calculation, but given the limitations of the temperature measurement, itís going to be close enough.

If you really wanted to get an accurate measurement, it would be very easy to model the freezing point based on the FG and ABV, and all you would need is vodka, water, table sugar, an accurate thermometer and scale, and enough free time to take 50ish data points.

I’m in science, FWIW... every time this comes up, people try to use the OG/FG equations to get the answer, and my point is, that those equations assume a "normal" strength brew (say less than 10% ABV final) and they are essentially useless for measurements of high-gravity brews or of anything where there was a concentration step.

If I offended you, I apologize. But the glycerol/water data aren’t even close to linear, even between 0-30%, about the range we’d be talking about for a high-gravity brew.

Iím in science, FWIW... every time this comes up, people try to use the OG/FG equations to get the answer, and my point is, that those equations assume a "normal" strength brew (say less than 10% ABV final) and they are essentially useless for measurements of high-gravity brews or of anything where there was a concentration step.

If I offended you, I apologize. But the glycerol/water data arenít even close to linear, even between 0-30%, about the range weíd be talking about for a high-gravity brew.

On the last point we agree.

I agree that OG/FG calculations break down for high ABV beers because the tables that people use aren’t appropriate for them. Granted, it would be very simply for a modified table or tables to be made that would be much more accurate.

Well, if you’re a Chemist, then you certainly would know better than me about freezing point depression calculations and their limitations, but it seems to me that a very good approximation could be made with it. Especially if you use the actual data to model the freezing point of sugar/water instead of assuming it’s linear. Again though, I don’t know the cut-off for those calculations and if any second order corrections are known, etc.

The sugar/water data doesn’t need to be linear to be useful, just need to be modeled accurately by a mathematical equation.

Originally posted by ryan
The sugar/water data doesnít need to be linear to be useful, just need to be modeled accurately by a mathematical equation.

And what kind of sugars - beer may have several. And what about the inclusion of proteins and alcohol? It might not have to be linear to be useful but it would have to, in some way, model the measured sample.